I suspect you used the IP address when you added that ESXi node to your vCenter.
Can you add the ESXi node with the FQDN?
i asked my network admin to make esxi access through FQDN..
now I can access the esxi in browser using fqdn..
but, in powercli if i use get-vmhost.. I dont get fqdn, instead I get IP
That's because the name (IP address) used to register the ESXi node in vCenter sits in the vCenter DB.
The best solution would be to unregister the ESXi node from vCenter, and then add it with the FQDN.